Add examples/minify

examples/minify/main.go

@@ -0,0 +1,92 @@
+// Copyright 2018 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build example jsgo
+
+// This example is an experiment to minify images with various filters.
+// When linear filter is used, mipmap images should be used for high-quality rendering (#578).
+
+package main
+
+import (
+	"bytes"
+	"image"
+	_ "image/jpeg"
+	"log"
+	"math"
+
+	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/ebitenutil"
+	"github.com/hajimehoshi/ebiten/examples/resources/images"
+)
+
+const (
+	screenWidth  = 640
+	screenHeight = 800
+)
+
+var (
+	gophersImage *ebiten.Image
+)
+
+func update(screen *ebiten.Image) error {
+	if ebiten.IsDrawingSkipped() {
+		return nil
+	}
+
+	ebitenutil.DebugPrint(screen, "Minifying images (Nearest filter vs Linear filter)")
+
+	for i, f := range []ebiten.Filter{ebiten.FilterNearest, ebiten.FilterLinear} {
+		y := 0
+		for j := 0; j < 12; j++ {
+			w, h := gophersImage.Size()
+
+			op := &ebiten.DrawImageOptions{}
+			s := 1.0 / math.Pow(2, float64(j)/2)
+			op.GeoM.Scale(s, s)
+			op.GeoM.Translate(32+float64(i*(w+4)), 32+float64(y))
+			op.Filter = f
+			screen.DrawImage(gophersImage, op)
+
+			y += int(float64(h)*s) + 4
+		}
+	}
+
+	return nil
+}
+
+func main() {
+	// Decode image from a byte slice instead of a file so that
+	// this example works in any working directory.
+	// If you want to use a file, there are some options:
+	// 1) Use os.Open and pass the file to the image decoder.
+	//    This is a very regular way, but doesn't work on browsers.
+	// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
+	//    This works even on browsers.
+	// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
+	//    This also works on browsers.
+	img, _, err := image.Decode(bytes.NewReader(images.Gophers_jpg))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Specifying filter on NewImage[FromImage] is just for backward compatibility.
+	// Now specifying filter at DrawImageOptions is recommended.
+	// Specify FilterDefault here, that means to prefer filter specified at DrawImageOptions.
+	gophersImage, _ = ebiten.NewImageFromImage(img, ebiten.FilterDefault)
+
+	if err := ebiten.Run(update, screenWidth, screenHeight, 1, "Minify (Ebiten Demo)"); err != nil {
+		log.Fatal(err)
+	}
+}